The summer solstice is meant to be a night and dawn of peace, love and amazement. But not all of those attending the celebrations at Stonehenge entered into the spirit of the event.

Druids, pagans and revellers watched as two men, one shirtless, staged a fist fight at the ancient monument in Wiltshire.

While the majority of the 18,000 people who attended the solstice celebrations were well-behaved, 20 arrests and almost 50 drug seizures were made.

Photographer David Hedges, who witnessed the fight, said: "They were sparring for a few minutes before they really started throwing punches."

Spectators surrounded the pair and a couple tried to break it up before the police arrived.

The 20 arrests included 11 for drugs offences and five for public order offences. Superintendent Gavin Williams of Wiltshire police said most of the attendees "came to see the sunrise in the spirit of the event. Although it was disappointing that some individuals chose to bring drugs with them, they were dealt with robustly."

Fewer people attended than in recent years, partly due to the damp weather, perhaps, but also because the event fell at the start of the week.

But Arthur Pendragon, a well-known druid who purports to be a modern incarnation of the legendary king, said both those who were there for faith reasons and the many others who attend just for a good time – including plenty who stopped off on the way to Glastonbury – seemed to have enjoyed the night and dawn.

He said: "We didn't get a great sunrise but it was dry. Everyone seems happy with the result."

The summer solstice is one of the occasions in the year when open access to the stones is allowed by English Heritage, custodians of the monument.

"It is great to see the stones being used in this way, as opposed to the usual manner with tourists being herded around," said Pendragon.

English Heritage said the atmosphere had been "peaceful and good-natured".